Radar devices are well known in the state of the art. They are more and more used in motor vehicles to allow the execution of driver assistance functions. Here, radar devices are used for the detection of the environment or of objects in standing and flowing traffic. As motor vehicle control intervention, such as engine intervention or brake intervention, can be executed on the basis of the data of the radar device, the reliable function of such radar devices are of high importance.
In a radar device, the routing of a local-oscillator signal (LO-signal) by a used oscillator, such as a 24 GHz-oscillator, is possible vial respective HF-lines for the mixers of the receiver channels.
This signal routing allows a coherent mixture of the received signal in an NF-frequency band and therefore also signal processing based on this for the detection of targets in the environment of the radar device. For this reason, the verification of the presence of a correct LO-signal at the mixer input is of great importance for the internal diagnosis of the radar device. A faulty generation of the LO-signal or malfunction-caused damping or interruption of the LO-line should therefore be reliably detected during sensor diagnosis to avoid undefined operation and to bring the device into a defined condition.
Current radar devices do not allow the checking of the LO-signal and the LO-lines. A defect in this area would be detected only with limited reliability due to the detection of the failure of one or more receiver channels.